Integrated fixed film activated sludge (IFAS) systems are hybrid biological wastewater treatment systems consisting of microbial activity in both suspended phase, as in conventional activated sludge systems, and a fixed (biofilm) phase. The fixed phase is included through the addition of solid media, often to conventional activated sludge reactors, which provides a surface for biofilm growth. The media used is typically some form of extruded, honey-comb like plastic media (e.g. BioPortzTM, Entex Technologies), or a series of mesh netting screens through which the waste stream flows (BioWebTM, Entex Technologies). The addition of IFAS media greatly increases microbial mass in biological reactors, which accelerates the removal rates of soluble contaminants and provides additional capacity relative to conventional systems in the same volume. A major motivation for the use of these systems is to cost-effectively increase plant capacity, particularly with respect to nitrification, which is thought to be encouraged because the IFAS media provides a relatively stable environment with a long solids retention time (SRT) for slow growing, nitrifying bacteria.
Questions and Answers About Integrated Fixed-Film/Activated Sludge (IFAS) in a BNR Pilot Plant